murkiness vs fug

murkiness and fug both are nouns.

Word	Noun	Adjective	Verb	Adverb
murkiness	Yes	No	No	No
fug	Yes	No	No	No

As nouns, fug is a hyponym of murkiness; that is, fug is a word with a more specific, narrower meaning than murkiness:

murkiness: an atmosphere in which visibility is reduced because of a cloud of some substance
fug: (British informal) an airless smoky smelly atmosphere

murkiness (noun)	fug (noun)
the quality of being cloudy	(British informal) an airless smoky smelly atmosphere
an atmosphere in which visibility is reduced because of a cloud of some substance